DT: Vendors: Add Everspin

Everspin is a vendor of MRAM devices. Add them to the list
of Vendors.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -56,6 +56,7 @@ epson	Seiko Epson Corp.
 est	ESTeem Wireless Modems
 eukrea  Eukréa Electromatique
 everest	Everest Semiconductor Co. Ltd.
+everspin	Everspin Technologies, Inc.
 excito	Excito
 fcs	Fairchild Semiconductor
 fsl	Freescale Semiconductor